A. Field of Invention
This invention relates generally to improvements to the delivery of drugs, particularly for osseous regeneration for the maxillary sinus. More specifically this invention provides a method and device to the elevation of the floor of the maxillary sinus to increase the amount of bone available based on using hydro-dissection to raise the subantral membrane floor of the sinus (a.k.a. the Schneiderian membrane) allowing placement of osseous regenerative materials.
B. Description of the Prior Art
Dental implants have been used in dentistry for about 20 years. They offer a tremendous benefit to patients by allowing the replacement of missing teeth. Prof. Per-ingvaar Branemark introduced the use of titanium dental implants that showed that predictable, stabile implant integration occurs when implants have sufficient contact with the surrounding bone. Initially the placement of dental implants were limited to the anterior lower jaw, as this region provided sufficient bone quantity, quality and strength to support and hold a dental implant having an effective length.
Dental implants have revolutionized the treatment of many patients who previously lost dental function as a result of losing teeth. Today's standards of care now dictate that tooth loss is best treated with dental implants which then could be used for supporting an appropriate dental appliance. The previous alternative of dental bridges is now considered an inferior alternative in comparison to dental implants.
The success of dental implants is based on a variety of factors including; surgical technique, health of the patient, operator skill and, to a significant part, sufficient bone for the placement and integration of dental implants. To that end, the replacement of the maxillary posterior teeth have presented a considerable challenge because, after the loss of maxillary posterior teeth the quality and quantity of the remaining supporting bone may be insufficient to support implants properly or reliably.
The maxillary complex is a three-dimensional bone structure composed of alveolar bone and basal bone. The teeth, and more specifically, the teeth roots are imbedded in the alveolar bone. The top of the structure forms the floor of the maxillary sinus and is covered by thin diaphanous membrane known as the subantral or Schneiderian membrane. Once a tooth is removed from the complex, the surrounding alveolar bone is frequently resorbed because of the lack of physical stimulation and support of the teeth. This leads to a loss of bone mass and a corresponding reduction in the effective height and thickness of the bone of the maxillary complex. In addition, with the loss of teeth from the upper jaw (and the maxillary complex) the compensatory enlargement of the maxillary sinus occurs that also reduces the vertical height of the remaining bone of the maxillary complex. These effects further compromise the option for dental implants to be used.
To overcome the deficiency of insufficient vertical bone mass of the maxilla, several surgical techniques have been developed to increase available bone mass for the replacement of dental implants by bone augmentation. The process includes augmenting the region with a filler or regenerative material made of natural and/or artificial (synthetic) materials by placement of these elements on the roof of the maxillary structure, under the subantral membrane so that it does not interfere with the function of the maxillary sinus.
Collectively, these procedures are known within the dental profession as “sinus elevation procedures” with the goal of increasing the vertical height available for placement of dental implants. What makes these techniques unique from other techniques, such as distraction osteogenesis, is that the bone is increased within a body cavity, i.e., the maxillary sinus cavity. The first of these surgical techniques requires a window into the maxillary sinus from a lateral and superior approach to the floor of the sinus. Great care must be taken during the entry to the sinus as it is critical not to perforate the subantral membrane that lines the sinus cavity. Bone augmentation of the maxillary sinus requires delicate dissection of the subantral membrane from the floor of the sinus. If the membrane is not properly dissected from the bone, bone augmentation may not occur, or may not be sufficient. Unintentional perforation of the subantral membrane may also lead to undesirable short and long-term consequences. If the perforation is large, for example, several millimeters in diameter, the surgeon must either abort the procedure or must use some means of containing the regenerative material placed on the floor of the sinus to encourage new bone growth. A lack of integrity of the membrane can also lead to the migration of regenerative bone materials leading to long-term chronic infections. Therefore, the maintenance of membrane integrity is of utmost importance during the elevation of the membrane to allow placement of regenerative materials with a goal of increasing bone mass in the maxilla.
Most patients and dental surgeons acknowledge that entrance into the maxillary sinus utilizing a lateral window approach (also known as the Caldwell-Luc procedure) is an invasive procedure. This technique is fraught with many risks and complications because of the limitations of healing potential in the maxillary sinus. In spite of these risks many patients undergo this procedure because of the strong desire to replace missing maxillary teeth with dental implants.
An alternative approach to the maxillary sinus from the inferior approach of the alveolar ridge utilizing solid cylindrical osteotomes was described by Dr. Summers. It is a more conservative approach and is less invasive. It was developed to eliminate the risks described above. This technique referred to as the “osteotome sinus elevation technique”, and it gains access to the floor of the sinus from an inferior approach directly through the remaining alveolar ridge. The technique vertically “lifts” the floor of the sinus, or more specifically, the subantral membrane via an infracture of the bony floor and placement of bone regenerative material from an inferior approach. The bone regenerative materials are actually used to raise the subantral membrane. The infracture can be performed using solid cylindrical osteotomes with specific diameters that are vertically advanced toward the maxillary sinus producing a mechanical lifting action on the membrane. The technique has a variety of shortcomings as well, including the ability to carefully dissect (or separate) the subantral membrane from the floor of the sinus. While, this technique is safer, an overzealous use of an osteotome during the placement of the regenerative material can result in the perforation of the subantral membrane with disadvantages discussed above.
More recently several new techniques have been introduced to overcome some of the limitations of the Summers osteotome technique. The new technique also uses an inferior approach to the membrane via the alveolar ridge. One such technique was presented by Dr. Emmanuel Sotirakas using a medical syringe to raise the floor of the sinus by injecting fluid. This technique has many deficiencies owing to the inability to properly adapt a standard medical syringe to an opening created in the bone. A second technique used to elevate the subantral membrane is taught by Dr. Geraldo Nicolau Rodriguez that using a catheter balloon placed under the subantral membrane of floor of the sinus. This procedure requires an infracture of the underlying bone similar to the Summer procedure or a lateral window approach previously described. The catheter balloon is passed through the maxillary complex and the balloon is inflated. During inflation the subantral membrane is separated and forced away from the bony bed. Unfortunately, tearing or ripping of the subantral membrane may still occur and it is difficult, if not impossible, to detect it during the inflation of the balloon. In fact a perforation or tear in the membrane may take place no matter how carefully the balloon is inflated. After the membrane is separated, the balloon is withdrawn and a regenerative material is injected under the membrane, in a manner similar to the Summer technique. If a tear has occurred, the bone regenerative material may be placed unintentionally by the operator into the maxillary sinus necessitating the need for surgical removal of the regenerative material. In addition to the methods described above, an additional technique described by Dr. Leon Chen called the “Hydraulic Sinus Condensing Technique” advocates using a small round bur to gain access to the floor of the sinus exposing the membrane. Using a second larger round bur provides access which results in the exposure of the membrane to condense regenerative material below the membrane. A stream of water from a dental handpiece is used to create hydraulic pressure to elevate the subantral membrane. This technique has multiple deficiencies owing to the inability to control the pressure and forces applied to the subantral membrane owing to the lack of precision of this technique.
These alternative techniques to the lateral window approach to the maxillary sinus have evolved out of a need to develop less invasive, more conservative means of increasing the height, volume and bone mass of the maxillary alveolar ridge by elevation of the subantral membrane within the maxillary sinus and then depositing a bone regenerative material beneath the membrane to augment the available bone volume available for implant placement within the maxillary sinus.
The deficiencies and limitations of current techniques for sinus elevation relate to primarily: (1) the inability of the operator to control the infracture (“green-stick fracture) of the bony floor and lateral window of the maxillary sinus, (2) the inability to carefully separate the membrane from its physical adherence off the floor of the maxillary sinus and (3) a lack of feedback indication or confirmation for the surgeon of a perforation or tearing of the membrane prior to the placement of regenerative materials. Overcoming these previous limitations in the technique of sinus elevation will reduce infection, bleeding, swelling, pain, suffering and failure when using dental implants in the maxillary sinus.
To summarize, the following are the deficiencies of previous methods and devices:
1. Traumatic invasive surgical procedures that include extensive mucogingival flap elevation methods to gain access to the surgical site.
2. The use of instrumentation that comes into direct physical contact with the subantral membrane with the risk of perforating or tearing the membrane during separation of membrane from the floor of the sinus.
3. The need to use a infracture, i.e. “green-stick” fracture of the floor of the sinus or lateral aspect of the sinus that could once again perforate or tear the delicate subantral membrane leading to failure.
4. Using previous methods there is a lack of subjective indication or feedback to the operator that the membrane has been torn or perforated during is separation and elevation from the floor of the sinus.
5. Inability to precisely control the infracture of the bone that is required to gain access to the floor of the sinus using previous methods.
6. Inability to precisely control the force used to raise the subantral membrane.
7. Inability to precisely control the delivery of the regenerative material and to determine weather a tear or perforation of the membrane has occurred during the placement of such regenerative material.
8. Difficulty in accessing the integrity of the membrane prior to the placement of the regenerative material that will be placed on the floor of the sinus.
9. Inability to create a seal between the delivery device, such as a syringe and the prepared bony site during the elevation of the membrane and delivery of regenerative materials beneath the subantral membrane.
If regenerative materials are placed within the maxillary sinus and a perforation or tear of the subantral membrane has been caused during surgery this regenerative material will act as a foreign body within the sinus leading to ominous sequela. Failure to contain regenerative materials in the maxillary sinus often lead to the need for additional surgeries to retrieve such materials and may require extensive medical follow-up to corrective this iatrogenic outcome.